Jerry Fodor presents a new development of his famous Language of Thought hypothesis, which has since the 1970s been at the centre of interdisciplinary debate about how the mind works. Fodor defends and extends the groundbreaking idea that thinking is couched in a symbolic system realized in the brain. This idea is central to the representational theory of mind which Fodor has established as a key reference point in modern philosophy, psychology, and cognitive science. The foundation stone of (...) our present cognitive science is Turing's suggestion that cognitive processes are not associations but computations; and computation requires a language of thought. So the latest on the Language of Thought hypothesis, from its progenitor, promises to be a landmark in the study of the mind. LOT 2 offers a more cogent presentation and a fuller explication of Fodor 's distinctive account of the mind, with various intriguing new features. The central role of compositionality in the representational theory of mind is revealed: most of what we know about concepts follows from the compositionality of thoughts. Fodor shows the necessity of a referentialist account of the content of intentional states, and of an atomistic account of the individuation of concepts. Not least among the new developments is Fodor 's identification and persecution of pragmatism as the leading source of error in the study of the mind today. LOT 2 sees Fodor advance undaunted towards the ultimate goal of a theory of the cognitive mind, and in particular a theory of the intentionality of cognition. No one who works on the mind can ignore Fodor 's views, expressed in the coruscating and provocative style which has delighted and disconcerted countless readers over the years. (shrink)

Fodor and Pylyshyn's critique of connectionism has posed a challenge to connectionists: Adequately explain such nomological regularities as systematicity and productivity without postulating a "language of thought" (LOT). Some connectionists like Smolensky took the challenge very seriously, and attempted to meet it by developing models that were supposed to be non-classical. At the core of these attempts lies the claim that connectionist models can provide a representational system with a combinatorial syntax and processes sensitive to syntactic structure. They (...) are not implementation models because, it is claimed, the way they obtain syntax and structure sensitivity is not "concatenative," hence "radically different" from the way classicists handle them. In this paper, I offer an analysis of what it is to physically satisfy/realize a formal system. In this context, I examine the minimal truth-conditions of LOT Hypothesis. From my analysis it will follow that concatenative realization of formal systems is irrelevant to LOTH since the very notion of LOT is indifferent to such an implementation level issue as concatenation. I will conclude that to the extent to which they can explain the law-like cognitive regularities, a certain class of connectionist models proposed as radical alternatives to the classical LOT paradigm will in fact turn out to be LOT models, even though new and potentially very exciting ones. (shrink)

The European Legacy, Volume 17, Issue 3, Page 400-401, June 2012.

Mental representations remain the central posits of psychology after many decades of scrutiny. However, there is no consensus about the representational format(s) of biological cognition. This paper provides a survey of evidence from computational cognitive psychology, perceptual psychology, developmental psychology, comparative psychology, and social psychology, and concludes that one type of format that routinely crops up is the language-of-thought (LoT). We outline six core properties of LoTs: (i) discrete constituents; (ii) role-filler independence; (iii) predicate–argument structure; (iv) logical operators; (...) (v) inferential promiscuity; and (vi) abstract content. These properties cluster together throughout cognitive science. Bayesian computational modeling, compositional features of object perception, complex infant and animal reasoning, and automatic, intuitive cognition in adults all implicate LoT-like structures. Instead of regarding LoT as a relic of the previous century, researchers in cognitive science and philosophy-of-mind must take seriously the explanatory breadth of LoT-based architectures. We grant that the mind may harbor many formats and architectures, including iconic and associative structures as well as deep-neural-network-like architectures. However, as computational/representational approaches to the mind continue to advance, classical compositional symbolic structures – that is, LoTs – only prove more flexible and well-supported over time. (shrink)

The target article attempted to draw connections between broad swaths of evidence by noticing a common thread: Abstract, symbolic, compositional codes, that is, language-of-thoughts (LoTs). Commentators raised concerns about the evidence and offered fascinating extensions to areas we overlooked. Here we respond and highlight the many specific empirical questions to be answered in the next decade and beyond.

It has been over thirty years since the publication of Jerry Fodor’s landmark book The Language of Thought (LOT 1). In LOT 2: The Language of Thought Revisited, Fodor provides an update on his thoughts concerning a range of topics that have been the focus of his work in the intervening decades. The Representational Theory of Mind (RTM), the central thesis of LOT 1, remains intact in LOT 2: mental states are relations between organisms and syntactically-structured (...) mental representations, and mental processes are computations defined over such representations. The differences between LOT 1 and LOT 2 are mostly differences of focus. Whereas LOT 1 had a number of targets—e.g. reductionism, behaviorism, empiricism, and operationalism—LOT 2 identifies “pragmatism” as the main enemy of the “Cartesian” kind of mentalism Fodor favors (pp. 11-12). Moreover, unlike LOT 1, a main aim of LOT 2 is to defend a theory of concepts that is atomistic and referentialist: lexical concepts lack structure, and their meaning is determined by their relation to the world and not by their relations to other concepts (pp. 16-20). In addition to new discussions of concepts and content, LOT 2 treats us to Fodor’s latest thoughts on compositionality, computationalism, nativism, nonconceptual content, and the causal theory of reference. Although those familiar with Fodor’s work over the last thirty years will find its main conclusions unsurprising, LOT 2 is nevertheless an exciting, breezily written book that’s full of stimulating arguments and (in standard Fodor style) immensely interesting digressions. In the Introduction, Fodor bundles together a number of distinct doctrines under “pragmatism”—e.g., that “knowing how is the paradigm cognitive state and it is prior to knowing that in the order of intentional explanation” (p. 10), and that “the distinctive function of the mind is guiding action” (p. 13). But it’s clear by Chapter 2 that his main target is “concept pragmatism,” according to which concepts are individuated by their inferential properties. Fodor’s “Cartesianism,” in contrast, has it that none of the epistemic properties of concepts are constitutive.. (shrink)

“What is the structure of thought?” is as central a question as any in cognitive science. A classic answer to this question has appealed to a Language of Thought (LoT). We point to emerging research from disparate branches of the field that supports the LoT hypothesis, but also uncovers diversity in LoTs across cognitive systems, stages of development, and species. Our letter formulates open research questions for cognitive science concerning the varieties of rules and representations that underwrite (...) various LoT-based systems and how these variations can help researchers taxonomize cognitive systems. (shrink)

I critically explore various forms of the language of thought (LOT) hypothesis. Many considerations, including the complexity of representational content and the systematicity of language understanding, support the view that some, but not all, of our mental representations occur in a language. I examine several arguments concerning sententialism and the propositional attitudes, Fodor's arguments concerning infant and animal thought, and Fodor's argument for radical concept nativism and show that none of these considerations require us to (...) postulate a LOT that is innate or otherwise distinct from spoken languages. Instead, I suggest that we maintain the more conservative hypothesis, supported by introspection, that some of our thoughts occur in the languages that we speak. (shrink)

Stephen Laurence and Eric Margolis have recently argued that certain kinds of regress arguments against the language of thought (LOT) hypothesis as an account of how we understand natural languages have been answered incorrectly or inadequately by supporters of LOT ('Regress arguments against the language of thought', Analysis, 57 (1), 60-6, J 97). They argue further that this does not undermine the LOT hypothesis, since the main sources of support for LOT are (or might be) independent (...) of it providing an account of how we understand natural language. In my paper I seek to refute both these claims, and reinstate the putative explanation of natural language understanding as a necessarily central part of the support for LOT. The main argument exploits the fact that Laurence and Margolis give too little weight to the ideas (a) that LOT might be innate (b) that for LOT supporters a semantic theory must apply to in-the-head tokens, not linguistic utterances. (shrink)

Fodor and Pylyshyn's (F&P) critique of connectionism has posed a challenge to connectionists: Adequately explain such nomological regularities as systematicity and productivity without postulating a "language of thought'' (LOT). Some connectionists declined to meet the challenge on the basis that the alleged regularities are somehow spurious. Some, like Smolensky, however, took the challenge very seriously, and attempted to meet it by developing models that are supposed to be non-classical.

Jerry Fodor’s arguments for a language of thought (LOT) are largely theoretical. Is there any empirical evidence that supports the existence of LOT? There is. Research on Global Aphasia supports the existence of LOT. In this paper, I discuss this evidence and why it supports Fodor’s theory that there is a language of thought.

This paper attempts to clarify and critically examine Fodor's language of thought (LOT) hypothesis, focusing on his contention that the systematicity of language use provides a solid ground for the LOT hypothesis. (edited).

There are towns in which language-of-thought (LoT) is the best game. But do we live in one? I go through three properties that characterize the LoT hypothesis: Discrete constituents, role-filler independence, and logical operators, and argue that in each case predictions from the LoT hypothesis are a poor fit to actual human cognition. As a hypothesis of what human cognition ought to be like, LoT departs from empirical reality.

Quilty-Dunn et al. maintain that language-of-thought hypothesis (LoTH) is the best game in town. We counter that LoTH is merely one source of models – always wrong, sometimes useful. Their reasons for liking LoTH are compatible with the view that LoTH provides a sometimes pragmatically useful level of abstraction over processes and mechanisms that fail to fully live up to LoT requirements.

In this paper we argue that the insistence by Fodor et. al. that the Language of Thought hypothesis must be true rests on mistakes about the kinds of explanations that must be provided of cognitive phenomena. After examining the canonical arguments for the LOT, we identify a weak version of the LOT hypothesis which we think accounts for some of the intuitions that there must be a LOT. We then consider what kinds of explanation cognitive phenomena require, and (...) conclude that three main confusions lead to the invalid inference of the truth of a stronger LOT hypothesis from the weak and trivial version. These confusions concern the relationship between syntax and semantics, the nature of higher-level causation in cognitive science, and differing roles of explanations invoking intrinsic structures of minds on the one hand, and aetiological or evolutionary accounts of their properties on the other. (shrink)

The view that infants possess a full-fledged propositional language-of-thought (LoT) is appealing, providing a unifying account for infants’ precocious reasoning skills in many domains. However, careful appraisal of empirical evidence suggests that there is still no convincing evidence that infants possess discrete representations of abstract relations, suggesting that infants’ LoT remains incomplete. Parallel arguments hold for perception.

We agree with the target article that assuming language-of-thought (LoT) is useful for the development of cognitive and developmental theories. We note that the target article is weak in its assumptions about development of LoT and possible existence of multiple LoTs. In response to these weaknesses, we outline several developmental principles for LoT development, showing how a developmental theory of LoT springs from probabilistic LoT. We suggest a system 1.5 of reasoning allowing interchange between Bayesian and logical rules (...) as it fits purposes or domain. (shrink)

A science of prelinguistic infant cognition must take seriously the language-of-thought (LoT) hypothesis. I show how the LoT framework enables us to identify the representational and computational capacities of infant minds and the developmental factors that act on these capacities, and explain how Quilty-Dunn et al.'s take on LoT has important upshots for developmental theory-building.

We distinguish the question whether only human minds are equipped with a language of thought (LoT) from the question whether human minds employ a single uniquely human learning mechanism. Thus separated, our answer to both questions is negative. Even very simple minds employ a LoT. And the comparative data reviewed by Penn et al. actually suggest that there are many distinctively human learning mechanisms.

Fodor and Pylyshyn (1988) have presented an influential argument to the effect that any viable connectionist account of human cognition must implement a language of thought. Their basic strategy is to argue that connectionist models that do not implement a language of thought fail to account for the systematic relations among propositional attitudes. Several critics of the LOT hypothesis have tried to pinpoint flaws in Fodor and Pylyshyn’s argument (Smolensky 1989; Clark, 1989; Chalmers, 1990; Braddon-Mitchell and (...) Fitzpatrick, 1990). One thing I will try to show is that the argument can be rescued from these criticisms. (Score: LOT 1, Visitors 0.) However, I agree that the argument fails, and I will provide a new account of how it goes wrong. (The score becomes tied.) Of course, the failure of Fodor and Pylyshyn’s argument does not mean that their conclusion is false. Consequently, some connectionist criticisms of Fodor and Pylyshyn’s article take the form of direct counterexamples to their conclusion (Smolensky 1989; van Gelder, 1990; Chalmers, 1990). I will argue, however, that Fodor and Pylyshyn’s conclusion survives confrontation with the alleged counterexamples. Finally, I provide an alternative argument that may succeed where Fodor and Pylyshyn’s fails. (Final Score: LOT 3, Visitors 1.). (shrink)

Jerry Fodor's arguments for a language of thought are largely theoretical. Is there any empirical evidence that supports the existence of LOT? There is. Research on Global Aphasia supports the existence of LOT. In this paper, I discuss this evidence and why it supports Fodor's theory that there is a language of thought.

Does thought precede language, or the other way around? How does having a language affect our thoughts? Who has a language, and who can think? These questions have traditionally been addressed by philosophers, especially by rationalists concerned to identify the essential difference between humans and other animals. More recently, theorists in cognitive science, evolutionary biology, and developmental psychology have been asking these questions in more empirically grounded ways. At its best, this confluence of philosophy and science (...) promises to blend the respective strengths of each discipline, bringing abstract theory to bear on reality in a principled and focused way. At its worst, it risks degenerating into a war of words, with each side employing key expressions in its own idiosyncratic way – or worse, contaminating empirical research with a priori dogmas inherited from outmoded philosophical worldviews. In Baboon Metaphysics (2007), Dorothy Cheney and Robert Seyfarth offer an analysis of baboon cognition that promises to exemplify the very best interaction of philosophical theory and empirical research. They argue that baboons have a language of thought: a language-like representational medium, which supports the sophisticated cognitive abilities required to negotiate their complex social environment. This claim is intended to be surprising in its own right, and also to shed light on the evolution of spoken language. Because our own ancestors likely lived in a similarly complex social environment, Cheney and Seyfarth propose that the earliest humans also developed language first as a cognitive medium, and that spoken language evolved as a means to express those thoughts. There are two potential difficulties here. First, ‘Language of Thought’ (LOT) is a term of art, with much associated theoretical baggage and often comparatively little careful exposition. Thus, evaluating the claim requires getting clearer about just what LOT implies in this context.. (shrink)

Jerry Fodor, LOT 2: The Language of Thought Revisited , New York: Oxford University Press, 2008, x+228, $37.95, ISBN 978-0-119-954877-4 Content Type Journal Article Pages 439-443 DOI 10.1007/s11023-009-9164-4 Authors David Cole, University of Minnesota-Duluth Department of Philosophy 369 A B Anderson Hall Duluth MN 55812 USA Journal Minds and Machines Online ISSN 1572-8641 Print ISSN 0924-6495 Journal Volume Volume 19 Journal Issue Volume 19, Number 3.

The purpose of this paper is to explore the merits of the idea that dynamical systems theory (also known as chaos theory) provides a model of the mind that can vindicate the language of thought (LOT). I investigate the nature of emergent structure in dynamical systems to assess its compatibility with causally efficacious syntactic structure in the brain. I will argue that anyone who is committed to the idea that the brain's functioning depends on emergent features of dynamical (...) systems should have serious reservations about the LOT. First, dynamical systems theory casts doubt on one of the strongest motives for believing in the LOT: principle P, the doctrine that structure found in an effect must also be found in its cause. Second, chaotic emergence is a double-edged sword. Its tendency to cleave the psychological from the neurological undermines foundations for belief in the existence of causally efficacious representations. Overall, a dynamic conception of the brain sways us away from realist conclusions about the causal powers of representations with constituent structure. (shrink)

There are two versions of the language-of-thought hypothesis (LOT): Representational LOT (roughly, structured representation), introduced by Ockham, and computational LOT (roughly, symbolic computation) introduced by Fodor. Like many others, I oppose the latter but not the former. Quilty-Dunn et al. defend representational LOT, but they do not defend the strong computational LOT thesis central to the classical-connectionist debate.

Quilty-Dunn et al. defended the reemergence of language-of-thought hypothesis (LoTH). My commentary builds up implications for the study of the development of our logical capacities. Empirical support for logically augmented LoT systems calls for the investigation of their logical primitives and developmental origin. Furthermore, Quilty-Dunn et al.'s characterization of LoT helps the quest for the foundation of logic by dissociating logical cognition from natural language.

In the appendix to Psychosemantics, entitled ‘Why There Still has to be a Language of Thought,’ Jerry Fodor offers several arguments for the language of thought thesis. The LOT, as articulated by Fodor, is a thesis about propositional attitudes. It comprises the following two claims: propositional attitudes are relations to meaning-bearing tokens — for example, to believe that P is to bear a certain relation to a token of a symbol which means that P; and the (...) representational tokens in question are quasi-linguistic — in particular, they have the constituent structure appropriate to a language. (shrink)

The core of the language of thought program is the claim that thinking is the manipulation of symbols according to rules. Yet LOT has said little about symbol natures, and existing accounts are highly controversial. This is a major flaw at the heart of the LOT program: LOT requires an account of symbol natures to naturalize intentionality, to determine whether the brain even engages in symbol manipulations, and to understand how symbols relate to lower-level neurocomputational states. This paper (...) provides the much-needed theory of symbols, and in doing so, alters the LOT program in significant respects. (shrink)

Where does a probabilistic language-of-thought (PLoT) come from? How can we learn new concepts based on probabilistic inferences operating on a PLoT? Here, I explore these questions, sketching a traditional circularity objection to LoT and canvassing various approaches to addressing it. I conclude that PLoT-based cognitive architectures can support genuine concept learning; but, currently, it is unclear that they enjoy more explanatory breadth in relation to concept learning than alternative architectures that do not posit any LoT.

This commentary seeks to supplement the case Quilty-Dunn et al. make for the psychological reality of languages-of-thought (LoTs) in two ways. First, it focuses on the reduced physical demands which LoT architectures often make compared to alternative architectures. Second, it embeds LoT research within a broader framework that can be leveraged to understand the evolution of LoTs.

Cognitive science has evolved since early disputes between radical empiricism and radical nativism. The authors are reacting to the revival of radical empiricism spurred by recent successes in deep neural network (NN) models. We agree that language-like mental representations (language-of-thoughts [LoTs]) are part of the best game in town, but they cannot be understood independent of the other players.

From Fodor and Pylyshyn’s celebrated 1988 systematicity argument in favour of a language of thought , a challenge to connectionist models arises in the form of a dilemma: either these models do not explain systematicity or they are implementations of LOT. From consideration of this challenge and of systematicity in domains other than language, defenders of connectionism have mounted a parallel systematicity argument against LOT which results in a new self-defeating dilemma, what I call here the systematicity (...) challenge challenge : either LOT does not explain nonlinguistic systematicity, or it is in no better position than its rivals to explain any systematicity, even linguistic systematicity. In this paper, first, I critically examine the SCC and some considerations that seem to support it. Second, I offer a response to the SCC by: showing that LOT was never meant to be a cognitive model restricted only to linguistic systematicity, and formulating a new argument in favour of LOT from nonlinguistic systematicity. Third, I argue that there is a central assumption underlying the SCC and maintain that it is mistaken. I conclude that the classical systematicity challenge continues to be fully valid for linguistic and nonlinguistic domains. (shrink)

I elaborate on Quilty-Dunn et al.'s integration of the language-of-thought hypothesis in social reasoning by outlining two discrepancies between the experimental paradigms referred to by the authors and the social world: Self-referential projection and deliberate thinking in experiments. Robust tests of the hypothesis in social reasoning should include observational, natural, and cross-cultural approaches.

According to the language of thought (LOT) approach and the related computational theory of mind (CTM), thinking is the processing of symbols in an inner mental language that is distinct from any public language. Herein, I explore a deep problem at the heart of the LOT/CTM program—it has yet to provide a plausible conception of a mental symbol.

The thesis of this paper is that the causal theory of mental content (hereafter CT) is incompatible with an elementary fact of perceptual psychology, namely, that the detection of distal properties generally requires the mediation of a “theory.” I shall call this fact the nontransducibility of distal properties (hereafter NTDP). The argument proceeds in two stages. The burden of stage one is that, taken together, CT and the language of thought hypothesis (hereafter LOT) are incompatible with NTDP. The (...) burden of stage two is that acceptance of CT requires acceptance of LOT as well. It follows that CT is incompatible with NTDP. I organize things in this way in part because it makes the argument easier to understand, and in part because the stage-two thesis—that CT entails LOT—has some independent interest and is therefore worth separating from the rest of the argument. (shrink)

There are two ways to understand any proposed properties of language-of-thoughts (LoTs): As diagnostic or constitutive. We argue that this choice is critical. If candidate properties are diagnostic, their homeostatic clustering requires explanation via an underlying homeostatic mechanism. If constitutive, there is no clustering, only the properties themselves. Whether deep neural networks (DNNs) are alternatives to LoTs or potential implementations turn on this choice.

As Quilty-Dunn et al. observe, the language-of-thought hypothesis (LoTH) has fallen out of favor in philosophy. I will support the arguments made for its rehabilitation by Quilty-Dunn et al. by reviewing old, but still potent arguments for LoTH, and briefly criticizing recent proposed alternatives to LoT, such as Frances Egan's deflationism and Eric Schwitzgebel's dispositionalism, revealing inadequacies in such antirepresentational, antisyntactic theories.

Object individuation provides a test case for the claim that infants already have a prelinguistic language-of-thought (LOT). By 12 months, infants represent several sortal-kinds: Object, agent, animate, and perhaps artifact. Infants have also encountered many words for object kinds, animals, people, and artifacts, therefore it remains a viable hypothesis that language learning may play a causal role in the acquisition of sortal-kinds, contra Quilty-Dunn et al.

The Language of Thought program has a suicidal edge. Jerry Fodor, of all people, has argued that although LOT will likely succeed in explaining modular processes, it will fail to explain the central system, a subsystem in the brain in which information from the different sense modalities is integrated, conscious deliberation occurs, and behavior is planned. A fundamental characteristic of the central system is that it is “informationally unencapsulated” -- its operations can draw from information from any cognitive (...) domain. The domain general nature of the central system is key to human reasoning; our ability to connect apparently unrelated concepts enables the creativity and flexibility of human thought, as does our ability to integrate material across sensory divides. The central system is the holy grail of cognitive science: understanding higher cognitive function is crucial to grasping how humans reach their highest intellectual achievements. But according to Fodor, the founding father of the LOT program and the related Computational Theory of Mind (CTM), the holy grail is out of reach: the central system is likely to be non-computational (Fodor 1983, 2000, 2008). Cognitive scientists working on higher cognitive function should abandon their efforts. Research should be limited to the modules, which for Fodor rest at the sensory periphery (2000).1 Cognitive scientists who work in the symbol processing tradition outside of philosophy would reject this pessimism, but ironically, within philosophy itself, this pessimistic streak has been very influential, most likely because it comes from the most well-known proponent of LOT and CTM. Indeed, pessimism about centrality has become assimilated into the mainstream conception of LOT. (Herein, I refer to a LOT that appeals to pessimism about centrality as the “standard LOT”). I imagine this makes the standard LOT unattractive to those philosophers with a more optimistic approach to what cognitive science can achieve.. (shrink)

In this paper, we consider a range of puzzles for demonstratives in the language of thought we had raised in our last philosophical conversation we had with Jerry Fodor. We argue against the Kaplan-inspired indexing solution Fodor proposed to us, but offer a Fodor-friendly account of the demonstratives in the language of thought in its stead, building on our account of demonstrative pronouns in English.

Currently, there is an increasing number of older population groups, especially in developed countries. This demographic trend, however, may cause serious problems, such as an increase in aging diseases, one of which is dementia whose main symptom consists in the decline of cognitive functioning. Although there has been ongoing pharmacological research on this neurological disorder, it has not brought satisfying results as far as its treatment is concerned. Therefore, governments all over the world are trying to develop alternative, non-pharmacological strategies/activities, (...) which could help to prevent this cognitive decline while this aging population is still healthy in order to reduce future economic and social burden. One of the non-pharmacological approaches, which may enhance cognitive abilities and protect against the decline in healthy older population, seems to be the learning of a foreign language. The purpose of this mini-review is to discuss recent findings about the effect of foreign language learning on the enhancement of cognitive functions among healthy older individuals. The findings, divided into three research areas, show that the learning of a foreign language may generate a lot of benefits for older individuals, such as enhancement of cognitive functioning, their self-esteem, increased opportunities of socializing, or reduction of costs. However, as Ware et al. (2017) indicate, any intervention program on foreign language learning should be well thought of and tailored to the needs of older people in order to be effective and avoid accompanying factors, such as older people’s anxiety or low self-confidence. Nevertheless, more empirical studies should be done in this area. (shrink)

The topic of this dissertation is what thought must be like in order for the laws and generalizations of psychology to be true. I address a number of contemporary problems in the philosophy of mind concerning the nature and structure of concepts and the ontological status of mental content. Drawing on empirical work in psychology, I develop a number of new conceptual tools for theorizing about concepts, including a counterpart model of concepts' role in linguistic communication, and a deflationary (...) theory of concepts' formal features. I also suggest some new answers to old problems, arguing, for example, that content realism is not hostage to a naturalized semantics. This dissertation can, as a whole, be read as a sympathetic re-evaluation of the language of thought hypothesis (LOT). LOT claims that thoughts are sentences in a mental language of computation, and are composed of meaningful, atomic symbols—concepts—which are individuated entirely by their formal features. Each chapter either defends various components of LOT from recent criticism, or fills in gaps in the theory. I begin the dissertation by introducing the language of thought project, and motivating and explaining each of its central components. In chapter 2, I discuss a recent competitor to atomism—neo-empiricism—and argue that it fails to meet several key desiderata on theories of concepts, and defend atomism from similar charges. In chapter 3, I argue against a view common to both philosophy and psychology: that concepts must be shareable. If true, atomism is in jeopardy. I find shareability to be unmotivated, and suggest an alternative counterpart model of concepts that does a better job of explaining the things shareability was supposed to explain. Chapter 4 takes up the question of what formal features are and how mental symbols are individuated. I develop a reductive account, arguing that formal features are certain sorts of physical properties and symbol types are sets of these properties. I turn to the topic of content in chapter 5, and defend a very strong version of content realism against recent criticism. (shrink)